Bio 251 Exam 3 2025/2026 Exam
Questions with 100% Correct Answers |
Latest Update
Which of the following most accurately lists the source of calcium required
for the complete contraction of cardiac muscle cells?
A) calcium comes only from the extracellular fluid (ECF) surrounding the
cells
B) calcium comes only from the sarcoplasmic reticulum (SR) of the muscle
cells
C) calcium comes from both the extracellular fluid (ECF) surrounding the
cells and from the sarcoplasmic reticulum (SR) of the muscle cells
,D) calcium comes from the mitochondria in the muscle cells
E) calcium comes from the nucleus of the muscle cells - 🧠 ANSWER ✔✔C)
calcium comes from both the extracellular fluid (ECF) surrounding the cells
and from the sarcoplasmic reticulum (SR) of the muscle cells
2) In smooth muscle cells, calcium entering the cell first binds to ____ ; this
complex in turn activates myosin light-chain kinase to initiate the
contraction mechanism.
A) troponin
B) tropomyosin
e) titin
D) actin
E calmodulin - 🧠 ANSWER ✔✔E) calmodulin
3) What is the function of the sodium-calcium exchanger, i.e., a type of
secondary active transporter, in cardiac muscle cells?
A) to depolarize the cardiac muscle cells so they contract
, B) to trigger the release of calcium from the sarcoplasmic reticulum (SR) to
cause contraction
C) to pump calcium from the extracellular fluid (ECF) into the cell to initiate
contraction
D)to remove calcium from the cell by transporting it to the extracellular fluid
(BCF), thereby relaxing the muscle
E) to activate troponin to initiate cross-bridge cycling, and therefore,
contraction - 🧠 ANSWER ✔✔D)to remove calcium from the cell by
transporting it to the extracellular fluid (BCF), thereby relaxing the muscle
Crossbridge cycling between actin and myosin in smooth muscle requires
_____
A) the binding of calcium to troponin to expose the myosin binding site on
the actin molecule.
B) By the phosphorylation (activation) of myosin heads of the thick
myofilaments by myosin light-chain kinase, thereby allowing them to bind
with actin
COPYRIGHT©NINJANERD 2025/2026. YEAR PUBLISHED 2025. COMPANY REGISTRATION NUMBER: 619652435. TERMS OF USE. PRIVACY
STATEMENT. ALL RIGHTS RESERVED
3
Questions with 100% Correct Answers |
Latest Update
Which of the following most accurately lists the source of calcium required
for the complete contraction of cardiac muscle cells?
A) calcium comes only from the extracellular fluid (ECF) surrounding the
cells
B) calcium comes only from the sarcoplasmic reticulum (SR) of the muscle
cells
C) calcium comes from both the extracellular fluid (ECF) surrounding the
cells and from the sarcoplasmic reticulum (SR) of the muscle cells
,D) calcium comes from the mitochondria in the muscle cells
E) calcium comes from the nucleus of the muscle cells - 🧠 ANSWER ✔✔C)
calcium comes from both the extracellular fluid (ECF) surrounding the cells
and from the sarcoplasmic reticulum (SR) of the muscle cells
2) In smooth muscle cells, calcium entering the cell first binds to ____ ; this
complex in turn activates myosin light-chain kinase to initiate the
contraction mechanism.
A) troponin
B) tropomyosin
e) titin
D) actin
E calmodulin - 🧠 ANSWER ✔✔E) calmodulin
3) What is the function of the sodium-calcium exchanger, i.e., a type of
secondary active transporter, in cardiac muscle cells?
A) to depolarize the cardiac muscle cells so they contract
, B) to trigger the release of calcium from the sarcoplasmic reticulum (SR) to
cause contraction
C) to pump calcium from the extracellular fluid (ECF) into the cell to initiate
contraction
D)to remove calcium from the cell by transporting it to the extracellular fluid
(BCF), thereby relaxing the muscle
E) to activate troponin to initiate cross-bridge cycling, and therefore,
contraction - 🧠 ANSWER ✔✔D)to remove calcium from the cell by
transporting it to the extracellular fluid (BCF), thereby relaxing the muscle
Crossbridge cycling between actin and myosin in smooth muscle requires
_____
A) the binding of calcium to troponin to expose the myosin binding site on
the actin molecule.
B) By the phosphorylation (activation) of myosin heads of the thick
myofilaments by myosin light-chain kinase, thereby allowing them to bind
with actin
COPYRIGHT©NINJANERD 2025/2026. YEAR PUBLISHED 2025. COMPANY REGISTRATION NUMBER: 619652435. TERMS OF USE. PRIVACY
STATEMENT. ALL RIGHTS RESERVED
3
